1. Field of the Invention
The present invention relates to a method for reading images and an apparatus for reading images and more specifically, to a method for reading images and an apparatus for reading images recorded on an original.
2. Description of the Prior Art
Conventionally, there have been widely used photosensitive materials such as color negative films, color reversal films for recording color images, each having a three layer structure comprising a blue sensitive emulsion layer containing a yellow dye-forming coupler to form yellow color, a green sensitive emulsion layer containing magenta dye-forming coupler to form magenta color, and a red sensitive emulsion layer containing cyan dye forming cyan dye-forming coupler to form cyan color coated superposedly on a support.
Conventionally, there have been used methods for reading color images recorded on these photosensitive materials, in which each of the developed cyan, magenta, and yellow dye images is irradiated with light having wavelengths at which each of these dyes has a high absorbance, so as to detect light quantities transmitted through or reflected from these dye images so that light absorbance of each color developed dye can be calculated to obtain the density of each color image.
On the other hand, the spectral absorbance characteristics of the developed color dyes are not flat, as shown in FIG. 1, and vary with wavelength of light, with the maximum density of 3.5 at the wavelength where the absorbance of each developed color dye has a peak.
Therefore, in order to read the color image in a good quality by using the above described method, it was necessary to determine the density of each color at a density of 3.0, or more preferably at the maximum density of 3.5, at a high SN ratio (for example, 60 dB at minimum, preferably 70 dB or more).
However, conventionally, to determine the density of each color of the color images to the density of at least 3.0 at a high SN ratio, it was necessary to process using expensive circuit parts over a long period of time.